Changes

Summary

1. clarified signature;
2. tuned;
3. more operations for Build_Log.Meta_Info: prefer explicit types;
4. more operations for Date and Time;
5. more accurate patterns --- reverting unused fc3ba0a1c82f;
6. remove unused/fragile option (amending db37cae970a6) --- universal_table requires pull_date tables;
7. prefer explicit option "build_log_verbose";
8. tuned whitespace;
9. additional build_log column "session_start", with implicit upgrade of database schema;
10. more robust build_start for master and workers (via database);
11. more accurate progress.now(), notably for Database_Progress;
12. update NEWS;
13. activate E 3.0 after testing by Martin Desharnais, see also db72d9920186 and 788f11af9822;